Fuel delivery systems for direct injection applications, such as, for example, fuel-injected engines used in various types of on-road and off-road vehicles, typically include a fuel source, one or more fuel rails and a plurality of fuel injectors associated with the fuel rail(s). In such applications, the fuel rail may include a plurality of apertures in which injector sockets or cups are affixed. The fuel injectors are then inserted into and coupled with the injector cups so as to allow for the fuel flowing from the fuel source to the fuel rail to be communicated to the fuel injectors. The fuel communicated to the fuel injectors is then communicated to the combustion chamber of the engine.
One drawback of such direct injection systems, however, is the amount of pressure attendant in the system (i.e., on the order of 10 MPa or more). This pressure results in a relatively large amount of force and different twisting or bending moments being applied to the components of the system, and the connections or couplings therebetween. Consequently, various types of coupling arrangements designed to withstand the pressure/force of these systems have been utilized for coupling the system components together (e.g., coupling the fuel source to fuel rail, a fuel rail to another fuel rail, and/or a fuel injector to the fuel rail). However, while generally proving adequate with respect to withstanding the pressure/force in the system, these arrangements have not been without their respective disadvantages.
For instance, with respect to the coupling of a fuel injector with the fuel rail, in one arrangement, the fuel injector is coupled directly to the fuel rail and sandwiched between the fuel rail and the cylinder head of the engine. In this arrangement, undesirable noise can be generated. One prior attempt at eliminating or at least reducing this noise has included suspending the injector from the fuel rail. In one such arrangement an O-ring seal and a fuel injector clip are used to seal the connection between the fuel rail and fuel injector, and to hold and retain the injector in the correct position, respectively. Accordingly, the sealing and retention functions are performed separately. While such an arrangement may reduce the noise in the system, it requires additional components (e.g., the O-ring and the clip), which in turn increases the cost of the overall system and makes the corresponding manufacturing process more difficult.
With respect to the coupling of two fuel rails together, or coupling the inlet of a fuel rail with the outlet of a fuel source, metal-to-metal high pressure tube fittings have been utilized. These fittings generally include a tubular member having a spherical, cone, or ball shaped member (so-called male fitting) affixed to either one or both ends of the tube, and a threaded nut that circumscribes and slides along the length of the tubular member. The threaded nut is configured for mating with a complementary threaded portion disposed on either a fuel rail inlet or a fuel source outlet. One drawback of these conventional fittings is that the ball member typically requires a machined shank that results in a thin cross-section at the point of attachment between the tubular member and the ball member. While such an arrangement is generally able to withstand the pressure in the system, because the shank has been required, additional machining operations and material, and therefore, cost and difficulty have to be added to the manufacturing process. Additionally, the attachment point between the tubular member and the ball member may have a reduced strength due to the reduced cross-section of the shank.
Therefore, there is a need for a coupling apparatus for high pressure fuel delivery systems that will minimize and/or eliminate one or more of the above-identified deficiencies.